1. Field of the Invention
This invention relates to an ink jet recording method, particularly to an ink jet recording method by use of plain papers generally used in offices, homes, etc.
2. Related Background Art
Heretofore, various ink jet recording method methods have been investigated and proposed. Among them, the ink jet recording method which performs recording according to the drop-on-demand system has been investigated because miniaturization of instruments is possible and also its application range is extremely wide, so that detailed investigations have been made about ink, paper, mechanism of printer, etc.
However, the ink jet printer of the drop-on-demand system of the prior art has several problems, and the greatest of all is that paper generally used in offices, homes and the like such as notebook, report paper, copying paper, letter paper, post card, etc. cannot be used.
To describe in more detail, when printing is performed on various papers as mentioned above by means of an ink jet printer of the drop-on-demand system, the printed ink is spread along the fibers of the paper and therefore the shape of dot becomes indefinite so as to generate the so called blurring, whereby fine ruled lines, fine letters, complicated Chinese characters defined as JIS second standard and the like will frequently become unclear.
Further, the papers as mentioned above are applied with the treatment called sizing in the paper making process so that blurring may be caused when a writing implement using an aqueous ink is used. When printing is performed by an ink jet printer, the ink will not penetrate the paper well, and the dryability (drying property) of ink at the printed portion becomes poor, involving problems for example, if the print is rubbed with the cover of the printer, it will be smudged, the ink to rub off onto a hand when the printed matter is touched with hand.
Accordingly, for the purpose of improving dryability and decreasing of blurring, various improvements have been made. For example, methods have already been attempted the method in which the pH of the ink is made strongly alakaline, etc., in which a large amount of a surfactant is added in the ink, in which a water-soluble polymer is added in the ink, in which drying fixing of ink is accelerated by providing a heating drying means and the recording paper is pre-heated and heated before and after printing, and in which fixing property is improved by varying the conveyance speed of recording paper as shown in U.S. Pat. No. 4,469,026, etc. The method of making the pH of the ink strongly alkaline has such drawbacks that it is dangerous when the ink is touched with hand, and also that both blurring and dryability are not good in some cases for papers using a certain kind of sizing agent. On the other hand, in the method of adding a large amount of a surfactant, troubles arose, such as severe blurring depending on the paper, the ink was pulled from the discharge opening formed face depending on the conditions of the printer head, thus failing to discharge ink, or on the contrary, the whole of the discharge opening formed face was wetted so that no ink was discharged, etc. Further, in the method of adding a water-soluble polymer, effects can be seen to some extent concerning blurring and dryability of printing, but the ink tends to be readily dried also at the orifice tip of the discharge opening of the printer head, and when the printer is left to stand in room for several minutes without being used, there ensues the problem that no normal discharging can be effected. When the heating drying means is employed, there are involved the problems of thermal influence on the recording head, namely the problem of poor ink discharge, or the problems of mechanical and, electrical disorders of the device, further, protection of operators from burning, etc., and countermeasures thereagainst are required. Thus, it cannot necessarily be said to be a good means.
Also, when color ink jet recording is performed by use of a plurality of heads for realizing color formation, problems arise, such as insufficient drying and fixing of ink on recoding paper, lowering in image quality due to blurring of the overlapped portion of color inks and the boundary portion, and the problem of wrinkling of recording paper due to poor ink absorption at the overlapped portion. Accordingly, solutions of these problems have been directed to improvement by development of a coating paper for ink jet recording having improved ink absorption, but, on the contrary, the components in the coating layer have caused adverse effects on image quality, such as lowering in color reproducibility, poor light resistance, etc., thus posing a new problem.